This research is a large-scale controlled investigation of relaxation techniques in the modification of mild essential hypertension. Particular emphasis is placed on evaluating factors contributing to both the process and outcome of the relaxation treatment procedures. The subjects will be 240 individuals from a large industrial setting whose blood pressures are in the mild hypertension range (diastolic blood pressure between 90 and 105 mm Hg). The subjects will be medically evaluated and assigned to one of 6 experimental groups. Those prescribed medication will be placed in the group: 1) Standard Medical Treatment with Hypertension Medication. Those subjects not prescribed medication will receive the standard medical treatment and be randomly assigned to one of five other groups: 2) Standard Medical Treatment without Hypertension Medication, 3) Relaxation Training, 4) Relaxation Training plus Generalization, 5) Biofeedback-Facilitated Relaxation Training, and 6) Biofeedback-Facilitated Relaxation Training plus Generalization. Data on psychological characteristics along with psychophysiological and biochemical reactivity to physical and cognitive stressors will be obtained at preintervention, postintervention, and one-year followup evaluations. The primary outcome measure, blood pressure readings, will be obtained at both worksite and clinic settings throughout all phases of the study.